These days it seems to me that everyone blabs about the blessing of microservices and the new architectural style. In most articles about the new glory architecture of microservices, it’s generally assumed, that Java EE is slow, dull and scales poorly. There seems to be a big misunderstanding about what Java EE really is. And I even assume that not many of the young believers in the new world of microservices have engaged much with the concepts of Java EE. I’m taking here three examples each developer is confronted with. And perhaps you will rethink of these scenarios in the light of Java EE. Continue reading →

In this article I want to explain an issue concerning the JPA OneToMany relationship which I was faced with in one of my own projects. Working with object -orientated languages like java we often model relationships between object in various cases. One of such relationships is the OnToMany relationship. For example an object ‘Server’ may have a relationship to an object ‘Configuration’. To make the ‘Configuration’ object generic we can model the JPA object in Java like this:

In my last blog I introduced the concept of a “Business Process Service Architecture – BPSA“. This architectural style can be used to design a business process running in a microservice architecture, even when all services are decoupled strongly as single verticals.

The idea of this concept is, that a separated microservice is running the “Overall-Business-Process” decoupled from the verticals. The business process reflects the workflows implemented in the organisation of an enterprise. These workflows may also be often non-technical and human-centric. For example, the shipment of a product is usually performed manually, but also impacts the technical layers. So the question is: How can we coordinate our vertical service layers to align them to an “Overall-Business-Process”?

I want to explain the concept of BPSA first on a scenario which I visualize with the help of BPMN 2.0. The scenario is based on the example that I used in my first blog. The BPMN model I show here, was created with the Eclipse modelling Tool Imixs-BPMN, but first of all, this model is independent of the later used workflow engine.

The Model shows four different workflows. One workflow for each vertical and the “Order Management” Workflow which reflects the Overall-Business-Process. The model is kept very simple to only show the key facts of the concept.

Starting a New Process Instance

The business logic of a vertical does not happen by itself. There is typically always a triggering event that starts the business process. In our example, this is the reception of a new order. A new order can be received manually by a phone call or an E-Mail, or automatically triggered by another IT system, e.g. a online shop software. So once a new order is received, we start a new instance of the “Order Management” Process with the task “Receive Order”. The BPMN event “new Order Process” immediately starts the sub-process called “Order”, which is presenting the micro-workflow of the vertical ‘Order Service’. This sub-process can for example callback the microservice to create a new order dataset in a database.

But this is not necessary the only way to start the process. It is also thinkable that the Order Service will start the “Order Management” Process by itself because it’s the piece of software receiving the order details. Or for example the external IT system could trigger both verticals – the “Order Service” and the “Order Management” Process. The important thing here is, that after we received a new order we start a new Instance of the “Order Management” Process which is triggering the other involved sub processes.

So when we go back to the model example, now we have two new process instances – the “Order” which reflects the status of the vertical “Order Service” and the “Order Management” process which indicates the status of the general enterprise business process. Both processes are tightly coupled, which corresponds to the enterprise business process. On the other hand, the workflow service itself may be loosely coupled to the verticals, e.g. by a asynchronous reactive programming style.

Monitoring the Business Process

Once a new instance of the “Order Management” Process was started, we can now monitor the process including the status of its sub-processes. For example a Workflow Management UI can provide the sales manager with status information about current orders. This person has typically a high-level view on the process with is reflected by the“Overall-Business-Process”. But also a back-end monitoring system can use the workflow service, for example to control the load of expected records in different databases. In both cases the workflow model can be extended with different tasks to detail the status of each process layer.

The Control of the Process

The interesting part of the example which I illustrate here, is how the process can be controlled by a microservice. As shown in the BPMN model, each vertical has its own sub-process model. And only the vertical assigned to a specific sub-process is allowed to trigger an event inside this process. The “Workflow Service”, on the other hand, controls and verifies the consistency of the business process along the BPMN model.

In our example the “Order Service” may trigger the event “finished” of the “Order” workflow once the service has created the order-record in an order-database. This event will immediately change the status of the “Order Management” Process from “Receive Order” to “Send Invoice”. As a result of this status change, a new sub-process assigned to the “Invoice Service” will be created by the “Wokflow Service”.

As the order sub-process is now completed, the OrderService will no longer be able to send the “finished” event to the WorkflowService. A workflow engine will typically throw an exception in case a process tries to trigger irregular events. As each vertical can also monitor its assigned sub-process, each microservice can read the model to check the internal status and possible events to be triggered. As a result the typical business logic of a microservice to verify an internal business model can be reduced dramatically. For example we can design each sub-process in a generic style and always provide an event for a success-case and an error-case.

The benefit is that we can now control the process fully by the WorkflowService and decouple the service from the business logic. On the other hand a human actor may also be involved in the main process model. For example a warehouseman will be informed by E-Mail from the workflow engine that he have to confirm the shipment of the product. He can manually trigger a corresponding action from the Workflow Management UI. As a result of such a manual event the workflow engine may trigger another microservice.

How to Change the Process

In a productive environment, a sub-process will possible consist of a lot of different tasks and events, which can be triggered by the assigned vertical and monitored by different actors. Also the “Order Management” Process will typically contain more events to control the process in various ways. For example the sales manager may be able to trigger a “Cancel” event to stop the order management process. This status change would immediately affect all sub-processes which will be disallowed to send any further events to the main-process.

The advantage of this concept is, that the process models can be changed during runtime, without the need to change the implementation of a single vertical. This makes the concept strong and flexible and takes care about the typical business needs of a changing enterprise – an agile organisation.

Conclusion

Of course, the implementation of a Business-Process-Service-Architecture can be tricky in various details. Much of what is today typically hard-coded in the business logic of a microservice will be now transferred into a process model. For this purpose, also experiences with BPMN are required. But the effects of BPSA can be impressive, especially when the workflow engine itself covers a lot of the business logic. For example, a human-centric workflow engine like the open source project Imixs-Workflow, can send E-Mail messages, provide a process history, or distributes tasks to different actors to be involved in the process. Finally the microservices become smaller and can now indeed decoupled from each other.

It is also possible to disable this option not for the complete workspace but for the affected EAR project. In this case you can enable the Project Specific Settings, and disable the ‘Java EE configuration’.

So you can use the Maven Java EE Integration still for other modules (e.g. Web, JPA). I have tested this with the new Eclipse Neon release.

Eclipse Mars is a great IDE which a lot of performance improvements against older versions of Eclipse. But I still have in some workspaces the problem that my Eclipse IDE hangs during validation of XML files of my Web Projects (e.g. web.xml or faces-config.xml). This problem is well known for the Eclipse IDE. To solve this problem in Eclipse Mars it is sufficient to disable the Validation of “XML Schema Files”.

and also disable the Option “Honour all XML schema location” for the XML Files validation.

If you disable this options, Eclipse will be faster after updating xml files.

It takes me some time to figure out the right way to deploy an artifact with Jenkins. After a successful build, I wanted to deploy the generated EAR file into a custom directory of my server. After trying several plugins the Artifact Deployer Plugin seems to me the best solution.

With this plugin installed you can add a ‘Post-Build-Action’ to your project. The Artefact location can be specified using the wildcards “**/*.war” or “**/*.ear”. In case of a Maven Project it’s not necessary to add a Base Dir location like it was in earlier releases. The ‘Remote File Location’ is just your target directory. You have also an option to disable the deployment in case the build failed.

So that’s it. If you know other solutions (especially for Wilfly) let me know.

If you think about modern architecture, you will possibly find that one of the best solution (for the moment) seems to be a microservice architecture. Microservices are a quite different approach as we followed in the past, where we often designed monolithic enterprise applications. In a monolithic application context a single software system is encapsulating the business-logic, the database-layer and the UI components. The Java EE architecture provides a perfect framework to build such kind of applications to be deployed and executed in a scalable and transactional application server environment.

But monolithic enterprise applications are sometimes difficult to maintain, even if only little changes need to be made to one of its components. This is one reason why the idea came up to split a monolithic application block into several microservices.

One of the question is, how to change the architecture from a monolith approach to a modern service based architecture? A good overview what this means can be read in Christians Posta’s Blog.

Vertical Services

At the first look it seems to be easy to separate business logic into isolated services. But often this approach ends with a closely spaced set of microservices, which are not really loose coupled. One of the reasons can be the database layer which survives as a monolithic block behind all the new microservices. This happens when we think that database objects are related to each other. And this is only a very realistic picture of our real business world. But this creates complex synchronization points between all of our services and teams and you have to coordinate all of the changes in the database layer. Often a database change caused by one service affects also other services.

One solution to solve this problem can be, dividing the functionality into cohesive “verticals”, which are not driven by technical or organizational aspects. Each vertical will have its own “business logic”, “database” and an optional “UI component”. With this approach, we don’t need to re-deploy the entire monolithic business-service tier, if we made changes to a single database object or a functionality of one of these verticals. Ideally, a single team can own and operate on each vertical as well.

Usually, it is recommended to control the synchronization between the services by sending events. The approach behind this idea is the “Reactive Programming” style. The communication between the services is realized in an asynchronous way . So the business logic of one service layer did not depend on the result of another service layer. A service may or may not react on a specific event. And this is the idea of loose coupling.

But does this fit your business requirements?

The “Business Process Service Architecture”

One problem with decoupling the business logic into separate services is the fact, that there still exists an “Over-All-Business-Logic” behind all these services. This is known as the “Business Process.” If, in our example above, the Order-Service, Invoice-Service and Logistic-Service are implemented as separate building blocks, there is still the general bussiness process of the “Ordering-Management” in the background defining states and business rules. For example if a product is ordered by a customer (Order-Service) the product may not be shipped (Logistic-Service) before an invoice was sent to the customer (Invoice-Service). So it is not sufficient, if the Invoice-Service and the Logistic-Service react asynchronously on a new event, triggered by the Order-Service, without reflecting the business process.

What we can do now, is defining separate events indicating each phase in the Order-Management-Process. For example the Order-Service can send an “Order-Ready-For-Invoice-Event” to signal that the invoice need to be send. And a new “Order-Ready-For-Shipment-Event” can be triggered by the Invoice-Service to indicate that the invoice for the order was sent to the customer and the product can be shipped. But now we have again created the same problem as we had before with the common database. We couple our services via specific event types which are reflecting our business process. The business process is now spread across various services.

To avoid this effect of tightly coupled services we can separate the business process itself as a service. This means that we move the Over-All-Business-Logic out of our services and provide a separate new service layer reflecting only the business process.

I will call this a “Business-Process-Service-Architecture”. In this architecture style each service layer depends on the business-process-service. Events are sent only between a vertical and the Business-Process-Service layer. Our Order-Service, Invoice-Service and Logistic-Service may or may not react on those process events. The advantage of this architecture is, that we now have one service which controls the ordering management process and is reflecting the state for each process instance. Each vertical can call the business-service layer to query the status of the Over-All-Business-Process and also use these workflow information for further processing. Also we can change our business process independent from our vertical service layers.

BPMN 2.0 and Workflow Engines

One of the most common technologies to describe a business process is the ‘Business Process Model and Notation’ – BPMN 2.0 standard. BPMN was initially designed to describe a business process without all the technical details of a software system. A BPMN diagram is easy to understand and a good starting point to talk about a business process with technician as also with management people. Beside the general description of a business process, a BPMN model can also be executed by a process or workflow engine. The Workflow Management System controls each task from the starting point until it is finished. So based on the model description the workflow engine controls the life-cycle of a business process. An example of a workflow engine which can be integrated into a Business Process Service Architecture is the Open Source project Imixs-Workflow.

Beside the general control of the business process, our new service can also collect any kind of meta information from our verticals. The service becomes the central information point in our microservice architecture. We can now change our business process model and integrate new verticals without affecting existing implementations. We have finally decoupled our services. This is one of the most important effects you can achieve with this architecture style. In a future article I will show an example how to integrate a Business Process Service based on a RESTfull service interface.